The purpose of this project is to study the cell surface membrane, how it may change in transformation to malignancy, either spontaneously, or as induced by SV40 virus. Currently research is carried out on 1) changes in glycoconjugates, including glycoproteins and sulfated glycosaminoglycans such as heparan sulfate, and correlation with cell growth properties in tissue culture and in vivo in the syngeneic and in the nude mice; 2) controls of expression and methods of purification of SV40 specific T antigens, surface antigens and tumor specific transplantation antigens (TSTA); 3) selection of phenotypic and genotypic revertant tumor cells which lose SV40; 4) study of "spontaneous" transformation of cells in culture and of the balance between such tumorigenicity and the SV40 TSTA in families of clonal cells with known genealogy.